Example of using Sass Variables

variables.scss

$siteWidth: 1024px;
$gutterWidth: 20px;
$sidebarWidth: 300px;

body {
  margin: 0 auto;
  width: $siteWidth;
}

.content {
  float: left;
  width: $siteWidth - ($sidebarWidth+$gutterWidth);
}

.sidebar {
  float: left;
  margin-left: $gutterWidth;
  width: $sidebarWidth;
}